“In this repository you’ll find the fully reversed source code for GTA III (master branch) and GTA VC (miami branch).”
Fans rebuilt two 20-year-old games from the binaries and made them run on Linux, FreeBSD and the Raspberry Pi. You still need the original game files. Rockstar never ported them there and never fixed the old bugs. The fans did both for free. Expect Take-Two’s lawyers to notice before its developers do.